On the evaluation of modular polynomials

We present two algorithms that, given a prime ell and an elliptic curve E/Fq, directly compute the polynomial Phi_ell(j(E),Y) in Fq[Y] whose roots are the j-invariants of the elliptic curves that are ell-isogenous to E. We do not assume that the modular polynomial Phi_ell(X,Y) is given. The algorithms may be adapted to handle other types of modular polynomials, and we consider applications to point counting and the computation of endomorphism rings. We demonstrate the practical efficiency of the algorithms by setting a new point-counting record, modulo a prime q with more than 5,000 decimal digits, and by evaluating a modular polynomial of level ell = 100,019.Comment: 19 pages, corrected a typo in equation (8) and added equation (9

In search of a human visual quality criterion for image data compression

Transmission of digital pictures is characterized by the large amount of data and the high correlation of the sources. This is the reason why decorrelative picture coding is generally processed before any digital picture transmission. In order to reach acceptable bit rates, an information limitation is, furthermore, unavoidable. The compression ratio of the coding scheme is fixed by an economical trade-off between the codec complexity and the transmission costs. This optimum is obviously also fixed by the picture quality to be reached. Presently, one of the main problems in image data compression is the search for a human visual quality criterion. Human visual quality criteria for digital TV pictures are described. It is shown how to use such quality criteria in order to optimize transform coding schemes quantization.Anglai

Waiting-time approximations for service systems with a polling table

Waiting-time approximations for service systems with a polling table seem extremely useful since they enable some form of optimization and moreover they lead to the ability to control the systems under consideration. In this paper a special group of priority polling sequences is considered; for such a group, explicit formulas are derived for the mean waiting times at individual stations. Based on these explicit formulas, a comparison of the performance of a given station (i.e. the priority station) under different polling sequences is presented.Anglai

A capacitive neural network for associative memory

Neural networks show interesting properties in vision problems, such as pattern or character recognition. However, the advantages of such networks (speed, convergence, . . .) are only fully exploited with dedicated processors. This paper presents a VLSI architecture for Hopfield-like fully interconnected networks. Its particularity is to use capacitors as synaptic connections in place of resistors or current sources. This network is programmed by a learning rule adapted to such networks where the dynamics of the connection weights is restricted to some discrete values. The feasibility of this architecture has been proved by an 8-neurons network built with discrete components.Anglai

Buried target signature extraction from ground penetrating radar signal based on the equivalence principle

Ground penetrating radar is poised to be a very valuable tool in the field of humanitarian demining. Recently a monostatic stepped-frequency continuous wave (SFCW) ground penetrating radar (GPR) has been developed for the characterization of the soil electromagnetic (EM) parameters epsi (dielectric permittivity), mu (magnetic permeability) and sigma (electric conductivity). The approach is extended here for the GPR signal extraction of buried targets. The equivalence principle is used to decompose the GPR signal in its soil and target-in-soil contributions. It permits the subtraction of the soil contribution from the total GPR signal, which provides the signature of the buried target. We have extracted clean frequency and time-domain signatures of a metallic sphere and a PMIN-2 plastic mine embedded in a multilayered medium at various moisture levels. The GPR signal of the metallic sphere has been simulated using the method of moments and shows good agreement with its measured counterpart.Anglai

High-efficiency backside contact solar cells with a self-aligned process and new texturization technique for silicon

A self-aligned process for back side contact solar cells has been demonstrated. It requires only one photolithography step without alignment, instead of 4 to 6. As a consequence, the fabrication cost of BSC solar cells has been highly reduced. Also, a texturization method using the HF-HNO/sub 3/ couple in an isotropic etching has been investigated. This method allows to obtain a surface of periodic V-grooves with controllable sidewall angles. This new texturization technique, which may be used with multicrystalline silicon as well, opens the way to a new light trapping structure.Anglai

Self-consistent simulation of nano scale SOI devices: the case of nano flash memory

This paper presents a simulation method for a wide variety of ultra small devices. It combines TSUPREM-4, MEDICI and the self-consistent solution of the Poisson and Schrodinger equations considering not only the fabrication process but also quantum mechanical effects. This method has been used to investigate the physics of an SOI nano flash memory device, which is composed of a triangular channel PMOSFET with a floating gate embedded in the gate oxide. The simulation shows that the control gate geometry first induces the formation of an inversion channel on the top of the triangle and, at higher gate voltages, on the two upper sides of the triangle. The programming and erasing simulations of the device reveal that the injection of eight holes to the floating gate causes the threshold voltage shift to -1.6 V.Anglai

Effect of quantum confinement in SOI single-hole transistors

SOI single-hole transistors with various designed pattern sizes have been fabricated by converting a quantum wire to an island (or multiple islands) contacted to the source and the drain. The Coulomb blockade effect has been observed. Quantum mechanics has been investigated by solving the Poisson and Schrodinger equations in a self-consistent manner. The results show that the lower ground-state energy of the hole in narrow constrictions serves as a potential barrier which results in a Coulomb blockade effect.Anglai

Improvement of sub-0.25 mu m fully-depleted SOI CMOS analog performance by thinning the Si film

The present work demonstrates that deep-submicron FD MOSFETs exhibit outstanding properties for analog applications, well superior to comparable PD or bulk Si devices, in terms of gain, frequency, noise, swing... performance, provided that full depletion is ensured in all modes of operation by correct process optimization.Anglai